U.S. patent application number 10/474649 was filed with the patent office on 2004-07-15 for device and method for the catalytic reformation of hydrocarbons or alcohols.
Invention is credited to Buhlert, Magnus, Hass, Ernst-Christoph, Plath, Peter Jorg.
Application Number | 20040136902 10/474649 |
Document ID | / |
Family ID | 26009095 |
Filed Date | 2004-07-15 |
United States Patent
Application |
20040136902 |
Kind Code |
A1 |
Plath, Peter Jorg ; et
al. |
July 15, 2004 |
Device and method for the catalytic reformation of hydrocarbons or
alcohols
Abstract
The invention relates to a process and an apparatus for
catalytically reforming hydrocarbons or alcohols to hydrogen in a
plurality of partial reactions. The plurality of partial reactions
are performed individually and/or in combinations of at least two
of the plural partial reactions in a microreactor network
comprising microreactors and channels formed between the
microreactors, starting substances and/or reaction products of the
plural partial reactions being conveyed through at least part of
the channels between reactor spaces of the microreactors. Reaction
progress of the plural partial reactions in the microreactor
network is controlled by way of process control means for
controlling process parameters.
Inventors: |
Plath, Peter Jorg;
(Langwedel, DE) ; Hass, Ernst-Christoph;
(Hauptstrasse, DE) ; Buhlert, Magnus; (Bremen,
DE) |
Correspondence
Address: |
SUTHERLAND ASBILL & BRENNAN LLP
999 PEACHTREE STREET, N.E.
ATLANTA
GA
30309
US
|
Family ID: |
26009095 |
Appl. No.: |
10/474649 |
Filed: |
February 23, 2004 |
PCT Filed: |
April 2, 2002 |
PCT NO: |
PCT/DE02/01184 |
Current U.S.
Class: |
423/651 |
Current CPC
Class: |
C01B 3/323 20130101;
C01B 2203/0288 20130101; C01B 2203/0866 20130101; Y02E 60/50
20130101; H01M 8/0662 20130101; C01B 2203/142 20130101; C01B
2203/044 20130101; B01J 2219/00889 20130101; C01B 2203/0277
20130101; C01B 2203/1235 20130101; B01J 2219/00869 20130101; B01J
2219/00986 20130101; C01B 2203/145 20130101; C01B 2203/0838
20130101; B01J 2219/00871 20130101; C01B 2203/047 20130101; C01B
2203/1082 20130101; B01B 1/005 20130101; C01B 2203/169 20130101;
C01B 2203/1623 20130101; C01B 2203/82 20130101; B01J 2219/00835
20130101; C01B 2203/0233 20130101; C01B 2203/066 20130101; B01J
2219/00995 20130101; C01B 2203/1619 20130101; C01B 3/583 20130101;
C01B 2203/141 20130101; B01J 2219/00873 20130101; C01B 2203/1276
20130101; C01B 2203/1217 20130101; C01B 2203/0844 20130101; C01B
2203/147 20130101; C01B 2203/1223 20130101; B01J 2219/00013
20130101; C01B 3/382 20130101; C01B 2203/0883 20130101; C01B
2203/1288 20130101; C01B 2203/1241 20130101; C01B 2203/1642
20130101; B01J 19/0093 20130101; C01B 2203/085 20130101; B01J
2219/00867 20130101; C01B 3/38 20130101; C01B 3/48 20130101 |
Class at
Publication: |
423/651 |
International
Class: |
C01B 003/26 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 12, 2001 |
DE |
10118618.5 |
Jul 31, 2001 |
DE |
10137188.8 |
Claims
What is claimed is:
1. A process for catalytically reforming hydrocarbons or alcohols
to hydrogen in a plurality of partial reactions Tk (k=1, 2, . . .
), characterized in that the partial reactions Tk are performed
individually and/or in combinations of at least two of the plural
partial reactions in a microreactor network comprising
microreactors Rn (n=1, 2, . . . ) and channels Kmj (m=1, 2, . . . ;
j=2, 3, . . . ) formed between the microreactors Rn, starting
substances and/or reaction products of the plural partial reactions
Tk being conveyed through at least part of the channels Kmj between
reactor spaces RRp (p=1, 2, . . . ) of the microreactors Rn, and in
that courses of the process of the plural partial reactions Tk in
the microreactor network are controlled by way of process control
means for controlling process parameters.
2. The process as claimed in claim 1, characterized in that the
process control means comprise regulator valves Vmj (m=1, 2, . . .
; j=2, 3, . . . ) in at least said part of the channels Kmj, and in
that the conveyance of the starting substances and/or reaction
products of the plural partial reactions Tk through at least said
part of the channels Kmj is controlled by actuating the regulator
valves Vmj.
3. The process as claimed in claim 1 or 2, characterized in that at
least one other reaction substance and/or a further quantity of one
or all of the starting substances is fed into one or all of the
channels Kmj so as to control the process parameters by way of
premixing.
4. The process as claimed in claim 3, characterized in that the
other reaction substance for control of the process parameters is a
gas which is fed in.
5. The process as claimed in any one of the preceding claims,
characterized in that the process parameters are controlled by way
of the process control means to carry out at least part of the
partial reactions Tk far from a reaction equilibrium.
6. The process as claimed in any one of the preceding claims,
characterized in that an additional reaction substance is produced
in a reactor space RRx (1.ltoreq.x.ltoreq.p) of a microreactor Rx
(1.ltoreq.x.ltoreq.n), is conveyed through one or more of the
channels Kmj from the reactor space RRx to at least one other
reactor space RRy (1.ltoreq.y.ltoreq.p, x.noteq.y), and is
processed in the other reactor space RRy.
7. The process as claimed in claim 6, characterized in that the
additional reaction substance is steam for vapor reforming in the
at least one other reactor space RRy.
8. The process as claimed in any one of the preceding claims,
characterized in that a reaction product is fed back through at
least one of the channels Kmj from one of the microreactors Rn to
another one of the microreactors Rn.
9. The process as claimed in any one of the preceding claims,
characterized in that one of the partial reactions Tk is carried
out in parallel in several ones of the microreactors Rn.
10. The process as claimed in any one of the preceding claims,
characterized in that the process control means comprise a
temperature control means, and in that the reactor spaces Rap are
heated and/or cooled individually by way of the temperature control
means.
11. The process as claimed in claim 10, characterized in that
adjustment of the temperature control means is effected in response
to the temperature measured in a catalyst layer in the reactor
spaces RRp.
12. The process as claimed in any one of the preceding claims,
characterized in that the microreactors Rn are formed in a base
block, and in that, for heating and/or cooling the microreactors
Rn, the base block is preheated and/or precooled by way of a based
block temperature control means.
13. An apparatus for catalytically reforming hydrocarbons or
alcohols to hydrogen in a plurality of partial reactions Tk (k=1,
2, . . . ), characterized by a microreactor network comprising
microreactors Rn (n=1, 2, . . . ), each including at least one
reactor space RRp (p=1, 2, . . . ), by channels Kmj (m=1, 2, . . .
; j=2, 3, . . . ) formed between the microreactors Rn for conveying
starting substances and/or reaction products of the plural partial
reactions Tk between the reactor spaces RRp of the microreactors
(R1 . . . Rn), and by process control means for controlling process
parameters of the plural partial reactions Tk.
14. The apparatus as claimed in claim 13, characterized in that at
is least part of the microreactors Rn are arranged as a linear
chain of successive microreactors.
15. The apparatus as claimed in claim 13 or 14, characterized in
that at least another part of the microreactors Rn are mutually
interconnected through the channels Kmj so that each microreactor
of the other part of microreactors Rn communicates with each other
microreactor of the other part of microreactors Rn by way of the
channels Kmj.
16. The apparatus as claimed in any one of claims 13 to 15,
characterized in that a catalyst each is disposed in at least part
of the reactor spaces RRp.
17. The apparatus as claimed in any one of claims 13 to 16,
characterized in that a gas inlet each is provided in at least part
of the channels Kmj for feeding a gas.
18. The apparatus as claimed in any one of claims 13 to 17,
characterized in that a regulating device each is provided in the
channels for controlling the flow rate.
19. The apparatus as claimed in any one of claims 13 to 18,
characterized in that the microreactor network is formed in a base
block.
20. The apparatus as claimed in claim 19, characterized in that the
base block comprises a temperature control means for
heating/cooling the microreactor network.
21. The apparatus as claimed in any one of claims 13 to 20,
characterized by a reactor block comprising microreactors R1 . . .
Rx (x<p) for reforming hydrocarbons or alcohols, and by a
downstream reactor block comprising microreactors Rx+1 . . . Rp for
selective CO oxidation.
22. The apparatus as claimed in any one of claims 13 to 21,
characterized in that the microreactor network has outer dimensions
of a few centimeters.
Description
[0001] The invention relates to the art of catalytic reforming of
hydrocarbons or alcohols.
[0002] The availability of hydrogen is the fundamental condition
for use of fuel cells in mobile and stationary applications. As the
use of fuel cells is becoming more frequent, for example, in
automobiles it makes sense to restrict the operation of the energy
generating units of the automobile to one energy source, such as
methanol, gasoline, or diesel fuel rather than feeding each energy
generating unit from a different source of energy, such as one for
the Otto carburetor engine for driving, diesel for the heating
system, and methanol for the fuel cell for air conditioning and
current supply. For this reason, attempts have been made to utilize
the customary fuels for the production of the hydrogen needed for
the fuel cell.
[0003] It is a well established process in industry to reform
higher hydrocarbons or alcohols to hydrogen. However, when applying
this reforming process to obtain hydrogen for fuel cells, the
equipment known to date still is rather big and, therefore, ill
suited for employment in mobile installations. The cause of another
problem in producing hydrogen for fuel cells by way of reforming
higher hydrocarbons or alcohols is the complicated nature of the
chemical processes that occur in reforming and the consequential
difficulty of conducting the reaction. Known aggregates for
reforming hydrocarbons or alcohols, therefore, comprise expensive
means of control and regulation to handle the complicated reaction
processes and thus are not suited for use in mobile installations,
such as automobiles.
[0004] It is, therefore, the object of the invention to provide an
improved process and apparatus for reforming higher hydrocarbons or
alcohols, such as gasoline (benzine), diesel fuel, methanol, or
methane, that will facilitate hydrogen production for a fuel cell
in mobile equipment, especially vehicles.
[0005] This object is met, in accordance with the invention, by a
process as recited in independent claim 1 and an apparatus as
recited in independent claim 13.
[0006] The provision and utilization of a microreactor network with
its microreactors and microchannels permit high selectivity in
influencing the various partial reactions which are intricately
interconnected in reforming hydrocarbons or alcohols. The small
dimensions of the reaction spaces in the microreactors make it
easier to regulate and keep under control the reactions taking
place and, therefore, reduce the necessary expenditure for
mechanical equipment.
[0007] It is another advantage that the microreactor network is
particularly well suited as a means for producing hydrogen for
non-industrial applications because the space requirement of the
apparatus has been reduced considerably in comparison with known
(industrial) installations. Apart from application in mobile
equipment, the hydrogen obtained from reforming also may be put to
use, for example, in fuel cells for housing energy supply
systems.
[0008] According to a convenient further development of the
invention the process control means comprise regulator valves Vmj
(m=1, 2, . . . ; j=2, 3, . . . ) in at least the part mentioned of
the channels Kmj, and the conveyance of the starting substances
and/or the reaction products of the plurality of partial reactions
Tk through at least the part mentioned of the channels Kmj is
controlled by way of actuating the regulator valves Vmj. In this
manner the flow of starting substances and/or reaction products
between the microreactors can be optimized so as to optimize the
chemical reactions for different applications.
[0009] In a further development of the invention, at least one
other reaction substance and/or a further quantity of one or all of
the starting substances is fed into one or all of the channels Kmj
so as to control the process parameters by premixing. This permits
targeted control of the course taken by reactions in the individual
microreactors. For example, the chemical equilibrium of a reaction
in one of the microreactors can be shifted by supplying a further
reaction substance or a further amount of one or all of the
starting substances. In the selective oxidation of CO to CO.sub.2,
the resulting H.sub.2/CO.sub.2 mixture under equilibrium conditions
(water equilibrium) is counteractive to the selective oxidation.
Now, if moistened air is fed through one of the channels it can act
to shift the water equilibrium in the preferred direction. A
preferred embodiment, for this reason, provides for supplying gas
as the additional reaction substance to control the process
parameters.
[0010] A convenient modification of the invention provides for
controlling the process parameters by process control means to
carry out at least part of the partial reactions Tk far off from a
reaction equilibrium. Reactions in the microreactors of the
microreactor network thus can be influenced purposively to yield
the desired reaction products.
[0011] Optimization of the chemical reactions in reforming
hydrocarbons and alcohols in order to increase the efficiency is
achieved, with an advantageous embodiment of the invention, in that
a supplementary reaction substance is produced in a reactor space
RRx (1.ltoreq.x.ltoreq.p) of a microreactor Rx
(1.ltoreq.x.ltoreq.n), is conveyed through one or more of the
channels Kmj from the reactor space RRx to at least one reactor
space RRy (1.ltoreq.y.ltoreq.p, x.noteq.y), and is processed in the
other reactor space RRy. Apart from the feedback of reaction
substances thus obtained, especially the backcoupling of thermal
energy between the various microreactors in the microreactor
network can be exploited for taking an advantageous influence on
the chemical reactions under way. For example, the thermal energy
generated in exothermic reactions may be drawn upon for stimulating
or controlling endothermic reactions in another microreactor so as
to conduct the reaction autothermically.
[0012] It is preferred to use steam as the additional reaction
substance for vapor reforming in the at least one other reactor
space RRy in the context of reforming hydrocarbons or alcohols. The
microreactor network thus allows targeted use of one of the
microreactors for producing additional reaction substances which
then are employed in one or more other microreactors to perform the
respective chemical reactions taking place in them.
[0013] Further optimization of the efficiency of the chemical
reactions which occur in reforming is achieved with a preferred
further development of the invention with which a reaction product
from one of the microreactors Rn is fed back through at least one
of the channels Kmj to another one of the microreactors Rn.
[0014] A preferred further development of the invention may provide
for a partial reaction Tk to be carried out in parallel in several
ones of the microreactors Rn if it is desired to offer certain
intermediate products in greater volumes. In this way the reaction
of certain starting substances may be increased, as desired.
[0015] According to a convenient further development of the
invention, the partial reactions taking place in the microreactors
of the microreactor network may be specifically targeted for
intervention by temperature control means incorporated in the
process control means and by using the temperature control means
for individually heating and/or cooling the reactor spaces RRp. In
this manner, the temperature characteristics of the partial
reactions in the reactor spaces RRp may be individually taken into
account.
[0016] With a preferred further development of the invention, the
microreactors Rn may be formed in a base block, and the base block
may be preheated and/or precooled by a base block temperature
control means for heating and/or cooling of the microreactors Rn.
This minimizes expenditure for adjustment of a given starting
temperature for the plurality of microreactors of the microreactor
network. Thus a reaction environment may be established which is
adapted to the respective application.
[0017] The advantages of the dependent apparatus claims correspond
to the respective process claims.
[0018] The invention will be described further, by way of example,
with reference to the accompanying drawing, in which:
[0019] FIG. 1 shows a microreactor network for catalytic
purification of a flow of hydrogen with carbon monoxide;
[0020] FIG. 2 shows a microreactor network comprising five
microreactors for reforming methanol;
[0021] FIG. 3 shows the microreactor network of FIG. 2, with a
downstream reactor chain for selective CO oxidation;
[0022] FIG. 4 shows the microreactor network of FIG. 2, with a
channel between microreactors R2 and R4 being closed;
[0023] FIG. 5 shows the microreactor network of FIG. 3, with a
channel between microreactors R2 and R4 being closed;
[0024] FIG. 6 shows another microreactor network for vapor
reforming of methane;
[0025] FIG. 7 is a diagrammatic representation of a microreactor
means, as seen from the side;
[0026] FIG. 8 shows a base plate of the microreactor means
illustrated in FIG. 7, as seen from the top;
[0027] FIG. 9 shows a cooling plate of the microreactor means
illustrated in FIG. 7, including a diagrammatic representation of
the thermal flux .PHI.; and
[0028] FIG. 10 shows a heater plate of the microreactor means
illustrated in FIG. 7, including a heater string.
[0029] FIG. 1 is a diagrammatic presentation of a microreactor
network comprising a plurality of microreactors R1 . . . R4. A
highly selective, multi-stage, heterogeneous, catalytic oxidation
is carried out in the microreactor network to convert the carbon
monoxide (CO) contained in a hydrogen gas into carbon dioxide
(CO.sub.2) without, at the same time, significantly oxidizing the
hydrogen (H.sub.2) as well. The microreactors R1-R4 each include a
reaction space RR1 . . . RR4. The reaction spaces RR1-RR4 are
interconnected by channels K12, K23, and K34. The reaction
substances are conveyed through the channels K12, K23, K34 between
the reactor spaces RR1-RR4. Preferably, the microreactors R1-R4 ate
designed as specified in the international patent application
PCT/DE 01/02509, presenting a catalytic pipe reactor through which
an H.sub.2/CO mixture flows. The microreactors R1-R4 and the
channels K12, K23, K34 are formed in a base block 1 in which heater
filaments 2 extend so that the base block 1 can be kept at a given
basic temperature. Chemical catalysts are disposed in each of the
reactor spaces RR1-RR4, as disclosed in the international patent
application PCT/DE 01/02509.
[0030] Not only is the temperature of the base block 1 controlled
by means of the heater filaments 2, what is more also the reactor
spaces RR1-RR4 can be heated individually so that their temperature
may be above the basic temperature of the base block 1. The
temperature in each of the reactor spaces RR1-RR4 is measured by a
respective temperature sensor 4. The data measured are collected
from the temperature sensors 4 to be processed by a control means
and then used for adjustment of the temperature through individual
heating of the reactor spaces RR1-RR4.
[0031] The channels K12, K23, K34 include gas inlets 5, 6 for
feeding further gases. Gases thus may be introduced ahead of each
reactor space RR1-RR4 to influence the chemical reactions taking
place inside. In the case of catalytic oxidation of CO to CO.sub.2,
moistened air and an H.sub.2/CO gas mixture are supplied through
the gas inlets 5, 6, respectively. This corresponds to controlled
forward mixing. This forward mixing is made use of for establishing
a state far from equilibrium in the entire microreactor network,
including the microreactors RR1-RR4, and maintaining that state.
This greatly increases the selectivity of the catalytic oxidation
from CO to CO.sub.2 in the presence of H.sub.2. Adding moistened
air through the gas inlets 5 and a suitable choice of the flow
velocity can help prevent equilibrium conditions from being
adjusted in the oxidation of CO to CO.sub.2.
[0032] The reactor spaces RR1-RR4 preferably are embodied by flat
cylinders having a diameter of about .ltoreq.2 cm and a height of
about .ltoreq.5 mm. The reactor spaces RR1-RR4 communicate linearly
through the channels K12, K23, K34. The channels K12, K23, K34
preferably have a width of about .ltoreq.3 mm and a height of about
.ltoreq.3 mm. This results in an overall size of the microreactor
network of no more than a few centimeters.
[0033] Carbon monoxide from the H.sub.2/CO gas mixture can be
oxidized catalytically with a high degree of selectivity in the
presence of great quantities of hydrogen. The hydrogen thus
purified is suitable to be used as fuel for fuel cells since the CO
content in the remaining gas is less than 100 ppm. It involves
little expenditure to maintain the microreactor temperature needed
for the reaction in the base block 1, including the individual
reactor spaces RR1-RR4 and the channels K12, K23, K34 because of
the small dimensions of the microreactor network. Use of a base
block 1 made of aluminum gives the microreactor network a very low
weight. The compact structure of the microreactor network,
moreover, lends itself to very low energy consumption in the
catalytic oxidation of CO. The base block 1 also may be made of
ceramics, especially in the form of foamed ceramics. This
embodiment has the advantage that ceramics is an electrically
nonconductive material which makes it easier to introduce the
heater filaments 2.
[0034] With this embodiment of a microreactor network, the
apparatus illustrated in FIG. 1 is especially well suited for use
in mobile fuel cell aggregates, for example in vehicles.
[0035] FIGS. 2 to 6 illustrate microreactor networks for
catalytically reforming alcohols or higher hydrocarbons (KW). In
contrast to the microreactor network shown in FIG. 1 where the
microreactors RR1-RR4 are coupled one after the other in the form
of a linear chain, the microreactors R1 . . . R5 in the
microreactor networks shown in FIGS. 2 to 6 present a more complex
structure where one microreactor may be connected to several other
microreactors and backcoupling between microreactors is
possible.
[0036] FIG. 2 shows a microreactor network for reforming methanol.
The starting substance methanol is introduced into microreactor R1
and evaporated. The evaporated methanol passes through channels K12
and K14 to microreactors R2 and R4. Methanol is catalytically
decomposed in microreactor R2.
[0037] Microreactor R4 communicates through a channel K24 with
microreactor R2, through a channel K14 with microreactor R1, and
through a channel K54 with microreactor R5. A water-gas-shift
reaction with premixing by methanol (methanol-vapor reforming) is
carried out in microreactor R4. The evaporated methanol reaches the
microreactor R4 through the channel K14. The products of the
catalytic decomposition of methanol in microreactor R2, and CO, and
H.sub.2 pass through the channel K24 to the microreactor R4. In
addition, superheated steam obtained from water in microreactor R5,
is supplied to the microreactor R4 through channel K54.
[0038] Also in microreactor R3 does a water-gas-shift reaction take
place, yet other than in microreactor R4, without premixing. To
this end, the microreactor R3 communicates through a channel K23 in
FIG. 1 with the microreactor R2 so that CO and H.sub.2 can be
directed to the microreactor R3. Superheated steam reaches the
microreactor R3 through a channel K53. The starting substances both
in microreactors R4 and R3 are CO, CO.sub.2, H.sub.2.
[0039] As may be taken from FIG. 2, the channels between the
microreactors R1-R5 each are provided with a regulator valve V12,
V13, V14 . . . whereby the conveyance of substances through the
channels either may be allowed or blocked. The regulator valves
marked by an arrow, such as V12 and V53 are open, while the other
regulator valves, such as V25 and V15 are closed.
[0040] FIG. 3 shows the microreactor according to FIG. 2, with
channel K24 blocked. This means that, in the microreactor network
as presented in FIG. 3, the methanol vapor reforming as well as the
water-gas-shift reaction are carried out without premixing in both
microreactor R3 and microreactor R4.
[0041] The microreactor networks illustrated in FIGS. 4 and 5
comprise the microreactor network shown in FIG. 2 and in FIG. 3,
respectively. In addition to the microreactor networks according to
FIGS. 2 and 3, respectively, the micreoreactor networks in FIGS. 4
and 5 comprise a downstream reactor chain of microreactors R6, R7,
and R8 for selective CO oxidation in the presence of hydrogen.
These microreactors R6-R8 are embodied by a linear reactor chain
similar to the microreactor network shown in FIG. 1, and they were
added in order to reduce the CO content of the starting gas mixture
of the reforming process. The products, CO, CO.sub.2, and H.sub.2,
leaving the microreactors R3 and R4 are passed through channels K36
and K46 into the microreactor R6. Through a channel 100, the
microreactor R6 as well as the microreactors R7 and R8 are supplied
with superheated steam from the microreactor R5 and with air which
is moistened by the steam. By these means it is intended to
diminish the influence of the H.sub.2/CO.sub.2 gas mixture
resulting from the selective oxidation of CO to CO.sub.2.
[0042] FIG. 6 shows a microreactor network comprising microreactors
R1-R7 to perform vapor reforming of methane. The vapor reforming of
methane essentially is carried out in that part of the microreactor
network which comprises the microreactors R1-R5. Microreactors R6
and R7 are connected downstream as a linear reactor chain for
purifying carbon monoxide. The mode of operation of the
microreactor network presented in FIG. 6 will be explained below
with reference to methane as an example. However, it may be adapted
for vapor reforming any desired hydrocarbons (KW).
[0043] The methane to be reformed is introduced in microreactor R1
where it is preheated. It is then passed through channel K13 into
the microreactor R3 where it is mixed catalytically with steam, the
result being partial reforming. The steam is fed from microreactor
R2 through channel K23 to microreactor R3. The partly reformed
methane subsequently is conveyed through channel K34 to
microreactor R4 where the reforming is continued at elevated
temperature. Steam is fed to the microreactor R4 through channel
K24. From microreactor R4, the reaction products, CO and H.sub.2 in
the form of a gas mixture, are passed to the microreactor R5. Here,
moistened air is added, as in the microreactors R6 and R7, for
catalytic purification of the hydrogen stream.
[0044] The carbon monoxide purification, i.e. the selective
oxidation of CO to CO.sub.2 in the microreactors R6 and R7 is an
exothermic reaction. The resulting heat is returned to the
microreactors R1-R4 since the processes occurring in those
microreactors (in R3 and R4) are endothermic and consequently need
energy to be supplied. That is especially true of the preheating of
methane in the microreactor R1 and of the process of evaporating
water in microreactor R2. True, this does not assure an entirely
autothermic reaction performance, but the heat balance obtained is
as best as possible.
[0045] The microreactors of the microreactor networks according to
FIGS. 2 to 6 are similar to the microreactors in the microreactor
network shown in FIG. 1 in terms of their individual dimensioning
and configuration. Also the channels between the microreactors of
the microreactor networks illustrated in FIGS. 2 to 6 correspond in
design to the channels shown in FIG. 1. Moreover, it is provided
that the microreactors according to FIGS. 2 to 6 preferably should
be formed in a common base block which is adapted to be heated or
cooled to a basic temperature, as explained with reference to FIG.
1. The base block is equipped with various heater means for
individually raising the temperature of the respective
microreactors to a temperature above the basic temperature. The
various heater means may be connected to control means which
control the respective heater means in response to a temperature
measured by a temperature sensor in the corresponding microreactor.
In the simplest case the respective heater means are a heater
filament disposed in the base block in the vicinity of the
associated microreactor. Thus it is possible to apply heat to the
specific area of the microreactors in which a catalyst is
present.
[0046] FIG. 7 is a diagrammatic side elevational view of a
microreactor means 70. Two base plates 71 and 72 are formed with
microreactors and channels (not shown) which interconnect the
microreactors. Respective cooling plates 73 and 74 are arranged
above and below the base plates 71 and 72, respectively. Respective
heater plates 75 and 76 are arranged above the cooling plate 73 and
below the cooling plate 74, respectively, to keep the microreactors
in the base plates 71, 72 at a given basic temperature. The
material of the base plates, heater plates, and cooling plates may
be any material which possesses suitable heat conductivity. In the
case of the microreactor means 70 the preferred material are
metals, specifically brass for the heater and cooling plates 75, 76
and 73, 74, respectively. The base plate 72 which accommodates the
catalyst material is made of a chromium-nickel steel which is
conveniently coated with the chemical catalysts. The base plate 71
preferably is made of copper to provide optimum conductivity.
[0047] The embodiment of the elements making up the microreactor
means 70 will be explained in greater detail with reference to
FIGS. 8 to 10. As shown in FIG. 8, the base plate 71 comprises a
microreactor network which includes fourteen reactor chambers RK1 .
. . RK14 in which methanol is catalytically reformed, followed by
CO purification. The base plate 71 has a length of a few
centimeters, preferably about 25 cm, and a width of a few
centimeters, preferably about 7 cm. The distance between the
reactor chamber RK1 and reactor chamber RK13 or reactor chamber
RK14 is about 16 cm. The spacing between adjacent reactor chambers,
e.g. between reactor chambers RK3 and RK4 or reactor chambers RK7
and RK8 is about 4 cm. The base plate 72 has the same structure as
base place 71. The dimensions indicated are examples, they may be
chosen to be smaller for further miniaturization of the
microreactor means 70.
[0048] The reactor chambers RK1 . . . RK14 are interconnected
through channels 80. Each reactor chamber RK1-RK14 has its own
heating system, being heated, for instance, by a cartridge type
heater, and it disposes of sensors in the form of thermocouple
elements to measure the temperature. The microreactor chambers
RK1-RK14 and the channels 80 between them correspond to the
microreactors and channels in the microreactor network shown in
FIG. 1.
[0049] In the microreactor means 70, methanol (CH.sub.3OH) and
water (H.sub.2O) are evaporated and subsequently catalytically
reacted (reformed) in a multi-stage process, including premixing by
methanol and water, to a mixture of hydrogen (H.sub.2) and carbon
dioxide (CO.sub.2). Thereafter, shares of carbon monoxide (CO)
contained in the gas mixture are reacted in another multi-stage
process by heterogeneous, catalytic oxidation to form carbon
dioxide, without hydrogen, at the same time, being oxidized, too,
in an amount worth mentioning.
[0050] Liquid methanol is injected into reactor chamber RK1, and
liquid water is injected into reactor chamber RK2. Air is fed into
the system of the microreactor chambers through gas inlets 81 and
passed on into the reactor chambers RK9 to RK14 through channels
issuing from the gas inlets 81. The liquid methanol is evaporated
in the reactor chamber RK1 and passed on into the reactor chambers
RK3 to RK6 through channels issuing from the reactor chamber RK1.
The liquid water is evaporated in the reactor chamber RK2 and
passed through the channels issuing from reactor chamber RK2 into
the reactor chambers RK3 to RK14.
[0051] The first stage each of methanol reforming (without
premixing) is carried out in the reactor chambers RK3 and RK4. The
second stage of methanol reforming takes place in reactor chambers
RK5 and RK6, with methanol and water each being premixed with the
reaction products from reactor chambers RK3 and RK4 (H.sub.2,
CO.sub.2, CO). Apart from methanol reforming, therefore, a partial
water-gas-shift reaction already takes place in the reactor
chambers RK5 and RK6. That provides an improved energy balance as
compared to one-stage methanol reforming since the heat released
during the exothermic water-gas-shift reaction is made available
directly to the strongly endothermic reforming process.
[0052] With steam added to them, the reaction products from reactor
chambers RK5 and RK6 are conveyed through the respective channels
into the reactor chambers RK7 and RK8. That is where the major part
of the water-gas-shift reaction of CO and H.sub.2O to CO.sub.2 and
H.sub.2 takes place, leaving a residual portion of CO. For the
residual CO content to be converted into CO.sub.2, a chain of
reactor chambers RK9, RK11, and RK13 is connected downstream of
reactor chamber RK7 and a chain of reactor chambers RK10, RK12, and
RK14 is connected downstream of reactor chamber RK8. It is
convenient to design the two reactor chamber chains RK9-RK11-RK13
and RK10-RK12-RK14 as described in the international patent
application PCT/DE 01/02509. In each of the reactor chambers RK9 to
RK14 not only the respective CO.sub.2/CO/H.sub.2 gas mixture but
also steam from reactor chamber RK1 and air are admixed. That leads
to a highly selective CO oxidation in the reactor chambers RK9 to
RK14, i.e. to an almost complete elimination of the CO share along
the reactor chambers RK9-RK11-RK13 and RK10-RK12-RK-14,
respectively, accompanied by simultaneous suppression of the
oxidation of hydrogen. The products, CO.sub.2 and H.sub.2, leave
the microreactor means 70 through the gas outlets 82 (cf. FIG.
8).
[0053] The reactions occurring in the reactor chambers at the
right-hand side of the base plate 71 in FIG. 8 (selective oxidation
in reactor chambers RK9 to RK14 and water-gas-shift reaction in
reactor chambers RK7 and RK8) are exothermic. That applies also to
the reactions in the reactor chambers RK5 and RK6. By contrast, the
reforming of methanol in reactor chambers RK3 and RK4 and partly
also the reactions in the reactor chambers RK5 and RK6 are
endothermic, i.e. they require heat. Heat must be supplied also for
evaporating methanol and water in the reactor chambers RK1 and RK2.
In order to provide the optimum heat balance, cooling plates 73 and
74, respectively, are disposed above and below the base plates 71
and 72, respectively (cf. FIG. 7). They are designed to create a
thermal flux 4 from the locations of the exothermic reactions to
the locations of the endothermic reactions and evaporation
processes. FIG. 9 illustrates the example of a cooling plate 73, as
seen from the top, including cooling plate zones KP1 . . . KP14
which are disposed below the microreactor chambers RK1 to RK14 in
the base plate 72. The thermal flux .phi. is indicated by
arrows.
[0054] In an advantageous embodiment provision may be made so that
the gases in the channels 80 are guided past one another in a way
transferring the energy from the exothermic reactions to the
endothermic reactions through heat exchange. That is achieved, for
instance, by an inverted arrangement of the reactor chambers
RK1-RK14 in the base plates 71 and 72, respectively.
[0055] Construction dimensions of the laboratory pattern make it
necessary to apply external basic heating in order to maintain the
microreactor network at a predetermined basic temperature. FIG. 10
is a top plan view of the heater plate 76. A heater string 100 is
laid around heater plate zones HP1 . . . HP14 which are located in
the heater plate 76 below the microreactor chambers RK1-RK14 formed
in the base plate 72. In this manner, the microreactor chambers
RK1-RK14 are heated from below. Heater plate 75 is designed like
heater plate 76 and positioned above the cooling plate 73 for
heating the reactor chambers RK1-RK14 in the base plate 71 from
above (cf. FIG. 7).
[0056] In addition to the fundamental heating of the base plates
71, 72 by means of the heater plates 75 and 76, respectively, each
reactor chamber RK1-RK14 can be heated individually so that the
temperature in a respective reactor chamber may be higher than the
basic temperature of the corresponding base plate 71 or 72.
Fourteen cartridge type heaters are employed for this purpose in
the microreactor means 70. Apart from measuring the temperature at
the head of each heating cartridge, the temperature in the reactor
spaces of the reactors R1 to R4 is measured individually by an
additional temperature sensor. The data thus obtained are polled
from the individual temperature sensors to be processed by a
control means (not shown) and utilized for readjustment of the
temperature through the individual heating of the reactor chambers
RK1 to RK14.
[0057] In an advantageous embodiment having reduced dimensions the
cartridge type heaters may be replaced by heater filaments which
are coated with a catalyst material. That saves energy, and the
fundamental heating of the base plate 71 or 72 may be reduced to a
lower temperature. Besides, an even better heat exchange balance is
to be expected.
[0058] The features of the invention disclosed in the specification
above, in the claims, and drawings may be essential to implementing
the invention in its various embodiments, both individually and in
any combination.
* * * * *